That's not his call, or anyone else's, but that of the market as a whole. There are few if any artificial barriers to success for a prospective competitor, except for their own unbridled greed and indifference to customer service.
In the technology sector, the greatest success stories have emerged not when one company executes flawlessly, but when one company executes competently in an environment where all of the other competitors act like barking idiots. You can't even count the number of times this has happened, but citing Microsoft, Google, and Apple should be enough to get the point across.
That's what's happening with Valve, IMHO. It's not that they are perfect... but when your competition is Electronic Arts, it's hard not to look good.
When I am talking about market fragmentation, I was referring to the electronic distribution market: I mean that a distribution platform that has a lesser offer but has exclusive (permanent one) because of a tied up with a specific publisher is very restrictive. I wouldn't have problem if, in this case, Valve and EA could agree to allow reselling of title through their respective distribution system.
Imaging that, going to your local super market (ASDA for an example) you could not find a major brand of cereals (Kellogs for the sake of argumentation). And that you would have to go to a direct competitor to find it (Tesco in this case). This is a fairly strait forward hurdle against a free market.
I don't think it's necessarily bad to have a few different distributors, after all it was not so long ago that people would get their meat and vegtables from different shops for example.
